Grease compositions containing an aryl oxy alkyl salt as a stabilizer



Patented Sept. 28, 1954' GREASE COMPOSITIONS CONTAINING ARYL OXY ALKYLSALT AS A STABILIZER Arnold J. Morway,

Clark Township,

Union County, and Paul V. Smith, Jr., Westfield, N. J., assignors toStandard Oil Development Company, a. corporation of Delaware No Drawing.Application April 7, 1952, Serial No. 281,046

6 Claims. 1

This invention relates to lubricating grease compositions and moreparticularly to anti-friction bearing lubricating greases which aresuitable for high temperature use. More particularly, the inventionrelates to high temperature greases prepared from lubricating oilthickened with an alkali metal soap of a higher fatty acid, inconjunction with an alkali metal salt of a lower molecular weight oxyacid.

It has been suggested in the prior art that for some purposes, it isadvantageous to combine certain metal salts, particularly the metalsalts of organic acids of low molecular weight, with the metal soapswhich are ordinarily employed as thickeners for lubricating greasecompositions. Various investigators have found that the addition ofmetal salts of the character referred to have utility for improvingstability and high temperature properties, and the like. There ap pearto be several theories as to the operation of such metal salts inconjunction with the metal soaps. One such theory is that the additionof salts of low molecular weight acids to soaps of relatively highmolecular weight results in the formation of a complex with superiorgrease thickening effect and improved stability.

Whatever may be the phenomena involved, the addition of salts of lowmolecular weight compounds appears to be particularly advantageous inconnection with greases of alkali and alkaline earth metal soap bases.The low molecular weight salts appear in many cases to improve thephysical structure of the grease. Compositions of this character areparticularly receptive to the action of oxidation inhibitors and it ispossible that the compositions themselves are more stable againstoxidation than greases thickened with soaps of high molecular weightcarboxylic acids alone, for example.

Suggestions in the prior art have included the use of metal salts of lowmolecular weight carboxylic acids which are saturated, such as aceticand propionic acids, and even more recently it has been suggested thatcertain of the lower unsaturated acids, such as acrylic acid, crotonicacid, and the like may be used as soap thickener adjuncts.

According to the present invention, the salts of certain low molecularweight oxy acids are highly useful as ingredients of lubricatinggreases.

It is the object of this invention, therefore, to prepare an improvedgrease suitable for antifriction bearing and related surfaces atelevated temperatures, i. e., temperatures in the neighborhood of from300 F. to 350 F. and even higher. A further object of the invention isto provide a lubricating grease composition comprising a lubricating oilthickened to a grease consistency with a combination of the alkali metalsoaps of high molecular weight aliphatic acids and alkali metal salts oflower molecular weight oxy acids, hereinafter to be described.

The low molecular weight oxy acids which are employed in this inventioncontain an ether linkage and in this respect are similar to furoic acid,which is a heterocyclic unsaturated acid containing an ether linkage ina 5-membered ring. In fact, greases prepared by employing salts ofalkoxy acids such as ethoxypropionic acid, methoxybenzoic acid, and thelike, are, in many re spects, similar to the excellent high droppingpoint greases prepared from furoic acid. Other acids containing oxygenare apparently quite different. For example, when the soap of levulinicacid is employed, as the thickening agent alone or in combination withhigh molecular weight acid soaps, greases are formed of relatively lowdropping point and poor structural characteristics. This would appear tobe due to the oxygen atom of ketonic linkage contained in the levulinicacid molecule. The soaps of saturated straight chain acids of 6 to 10carbon atoms having no oxygen in the hydrocarbon chain, such as caproicacid, do not form greases due to their diificulty of satisfactorydispersion. In addition, mixtures of soaps of levulinic acid andstraight chain aliphatic acids are difiicult to disperse in mineral oileven at elevated temperatures, whereas the mixtures of the grease soapsand the salts of the oxy acids of this invention have a high degree ofdispersability.

Grease formulations containing the salts of the oxy aromatic acids suchas p-methoxybenzoic acid, have the added advantage of a low degree ofwater solubility and will wet metallic surfaces covered with water.These grease iormulations are also much more adhesive to metal surfacesthan other type greases.

The structure of some of the oxy acids mentioned above are shown below:

Molecular Weight 118 CH3-CHr-O-CHzCH2COOH Ethoxypropioic acid 112OCH=CHOH=OCOOH Furoic acid 116 CHa-( 3CH2CHz-COOH Levulinic acid 116CH3-CHzGH2-OH1CH2-COOH Caproic acid 152 oH3oC co0H Anisic acidEthoxypropionic acid may be prepared from beta-propiolactone by reactionwith ethyl alcohol. The beta-propiolactone may be prepared fromformaldehyde and ketone. The preparation of this acid is described inthe Journal of American Chemical Society, vol. 70, pages 998-1006 (1943)It may also be prepared by adding ethanol to acrylonitrile or acrylicesters followed by hydrolysis or by the reaction of an alkali ethoxidewith beta-halopropionic acid.

The oxy acids which are employed in the greases of this invention havethe following general formula:

R representing a saturated aliphatic radical having from 1 to 5 carbonatoms such as methyl, ethyl, propyl, isopropyl, n-butyl, iso-butyl, sec.y -b y yl, etc., or an aromatic radical having from 6 to 10 carbon atomssuch as phenyl, tolyl, Xylyl, t-butylphenyl, etc., R representing adivalent radical as selected from the group above.

Specific mention may be made of such compounds as methoxypropionic acid,ethoxypropicnic acid, nand isopropoxypropionic acid, nandisopropoxyacetic acid, seccndarybutoxyacetic acid, p-methoxybenzoicacid, p-ethoxybenzoic acid, phenoxyacetic acid, beta-phenoxypropionicacid, phencxybenzoic acid, and the like.

As has been stated before, the grease compositions of this invention areformed by combining with the desired lubricating oil an alkali metalsalt of a low molecular weight oxy acid with an alkali metal salt of ahigh molecular weight substantially saturated aliphatic acid. Ingeneral, the metallic element of the salts as well as of the soaps maybe any of the alkali metals. Sodium, however, is the preferredembodiment of the invention. It is within the concept of the invention,however, to use mixtures of sodium and lithium, i. e., the sodium saltof the low molecular weight oxy acid may be used in conjunction with thelithium soap of the high molecular weight saturated fatty acid and viceversa.

The relative proportions of the high molecular weight soap and of thelow molecular weight salt may be varied rather widely. In molecularproportions, it is preferred to use 1 to 3 parts of the soap with about1 to 2 parts of the salt. In general, however, it is preferable that themolecular proportions be more nearly equal and specifically, proportionsof about 1 to 1 appear to be the most satisfactory. Further, thequantity of the soap and salt ingredients to be used in a given greasecomposition vary with the type of grease which is desired and also withthe kind and the viscosity of the oil which is used as a liquid base.

For a stifi grease composition, the total quantity of soap and salt mayapproach 50% of the weight of the final composition. On the other hand,for a soft grease, the total proportion of soap and salt may be as lowas about 5% based on the weight of the entire composition.

In general, the grease should consist of a lubricating oil having aviscosity of about 35 to 200 SUS at 210 F. containing about 3 to 20 Or30% by weight of the metal soap of a C12 to C22 fatty acid or glyceridealong with 2 to 15 or 20% by weight of the metal salt of the lowmolecular weight oxy acid. In general, ethoxypropionic acid is preferredto form the low molecular weight oxy acid portion. However, as it waspointed out above, other oxy acids, such as methoxypropionic acid,propoxypropionic acid, pmethoxybenzoic acid, and the like, may be used.

For ordinary anti-friction bearing greases, the sodium soap and thesodium salt of ethoxypropicnic acid are specifically preferred.

In the preferred embodiment of this invention a substantially saturatedfatty acid having an average chain length in the range of 12 to 22carbon atoms is utilized, however, any of the fatty acids known in theart of grease manufacture may be employed. For ease of dispersion,generally the higher molecular weight acids are preferred. Thesepreferred acids consist predominantly of acids having a carbon chainlength of 18 or slightly higher. They may be natural products such asstearic, arachidic, or the hydrogenated acids obtained from tallow orfish oil acid fractions.

For the liquid phase of the grease, mineral base lubricating oils arepreferred but the invention is not necessarily limited to the mineralbase oils. Various synthetic oils may also be used. As is well known inthe art of grease making, certain synthetic esters, especially thedibasic acid esters, such as di-2-ethylhexyl sebacate and homologous andanalogous esters are preferred for certain purposes in grease making.According to this invention, the lithium soap grease of such compounds,modified with the sodium or lithium salts of ethoxypropionic acid, andthe like, are particularly useful for lubrication at very lowtemperatures. Other synthetic oil base greases such as those employingthe polyglycols or the glycol others are also contemplated as beingwithin the scope of this invention. The combined soaps and salts may beused to thicken mixtures of mineral oil and synthetic oil as well asbeing useful with either type of oil alone.

An example of the concept of this invention, a grease compositioncontaining the ethoxyprcpicnic acid and its properties are describedbelow:

EXAMPLE I a. Formulation Ingredients: Per cent weight Ethoxypropionicacid 6.0 Hydrogenated fish oil acids 15.0 Sodium hydroxide 4.4 Phenylalpha naphthylamine 1.0

Mineral lub. oil of 500 SUS vis. at F. (55 at 210 F.) 73.6

1). Method of preparation The hydrogenated fish oil acids and A; of themineral oil were charged to a fire heated grease kettle and thetemperature raised to F. The ethoxypropicnie acid was charged and theacids immediately coneutralized with a 30% aqueous Properties:

Percent free alkali 0.12 as NaOH. Appearance yellow-smooth short fiber.Dropping point F 446. Worked penetration mm./ 306. Structure stabilityto mechanical 339 mm./l0.

working penetration after 100,000 strokes fine hole worker plate.

Water washing test-Percent loss (125 0.0.

F. water temperature). Wheel bearing test, 6 hours at 220 F.... Pass,conditions and lubrication excellent. High temperature spindle test 204400 hours before bearbearing, 10,000 R. P. M.300 F. ing failure Greasestill in good condition.

EXAMPLE II a. Formulation Percent Ingredients: weight Anisic acid 5.00Hydrogenated fish oil acids 10. 00

Sodium hydroxide Phenyl-alpha-naphthylamine Mineral lubrication oil of50 (50 SUS at 210 F.)

b. Method of manufacture The anisic acid, fish oil acid and /3 of themineral oil were charged to a fire heated grease kettle and heated Whileagitating to 150 F. The sodium hydroxide as a 30% aqueous solution wasadded and the soaps formed dehydrated while heating to 300 F. Thebalance of the mineral oil was then gradually added while continuing toheat to 450 F. At this temperature the phenylalpha-naphthylamine Wasadded and the grease drawn into pans for cooling. (It may be left in thekettle to cool.) When cool the grease was broken down by stirring in thekettle and homogenized. The free reaction of the grease may vary from0.5% as oleic acid to 0.5% as NaOH. Greases varyin between these limitsare of excellent structure and stability.

water; unaffected at temp. up to 185 F. Tendency to displace water on awet Displaces water and metal surface. clings to metal surfaces.Norma-Hoffman bomb, oxidation hours 385.

to 5 p. s. i. drop at 210 F. (hours).

EXAMPLE III a. Formulation Percent Ingredients: weigf t Anisic acid 3.45

Hydrogenated fish oil acids 7. 50 Sodium hydroxidePhenyl-alpha-naphthylarninc 75 0 Mineral lubrication oil of 500 SUSvisc. at 100 F. (50

SUS at 210 F.) 85.60

b. Method of manufacture The anisic acid, fish oil acid and A; of themineral oil were charged to a fire heated grease kettle and heated whileagitating to 150 F. The sodium hydroxide as a 30% aqueous solution wasadded and. the soaps formed dehydrated while heating to 300 F. Thebalance of the mineral oil was then gradually added while continuing toheat to 450 F. At this temperature the phenyl-alphanaphthylamine wasadded and the grease drawn into pans for cooling. (It may be left in thekettle to cool.) When cool the grease was broken down by stirring in thekettle and homogenized. The free acidity of the grease may vary from0.5% as oleic acid to 0.5% as NaOH. Greases varying between these limitsare of excellent structure and stability.

Properties:

Penetrations, mm./10 77 F UnworkecL 220. Worked 60 strok 225. Worked100,000 strokes (fine hole 275.

worker plate) Dropping Point, F 500+. Water resistance Soluble inboiling water; unafiected at temp. up to 185 F. Tendency to displacewater on a wet Displaces water and metal surface. clings to metalsurfaces. Norma-Hofiman bomb,oxidationhours 385.

to 5 p. s. i. drop at 210 F. (hours).

EXAMPLE IV a. Formulation Percent Ingredients: weight gethoxy benzoicacid... 5.0 ydrogenated fish oil ac 10. 0 Sodium hydroxide 3. 0Phenyl-alpha-naphthylam 1. 0 Mineral lubricating oil of 500 SUSviscosity at F. (50

SUS at 210 F.) 81.0

b. Method of manufacture This grease composition was prepared accordingto the procedure described in Example III(b) above.

EXAMPLE V a. Formulation Percent Ingredients: weight Phenoxy acetic acid5. 0 Stearic acid Sodium hydroxide 3. 2 Phenyl-alpha-naphthylarnineMinegall lpbricating oil of 500 SUS at 100 F. (50 SUS at 210 b. Methodof manufacture The grease of this example was prepared by the proceduredetailed in Example III(b) above.

Properties:

Penetrations, 111111.]10, 77 F.:

Unworked 200. Worked 60 strokes 210 Worked 100,000 strokes (fine workerplate) Dropping point, Water resistance Norma-Hellman oxidation test rsto 5 p. s. i. pressure drop at 210 F) 295.

EXAMPLE VI a. Formulation Ingredients:

Beta-phenoxy propionic acid Hydrogenated fish oil acids Sodium hydroxidePhenyl-alpha-naphthylamme Mineral lubricating oil of 500 SUS at 81.0

100 F. (50 SUS at 210 F.).

Percent weiahot b. Method of manufacture The grease sample was preparedin accordance with Example III(b) above.

Properties:

Penetrations, rum/10, 77 F;

Unworked 205. Worked 60 strokes 215. Worked 1000,000 strokes (fine hole265.

Worker plate). Dropping point, F 500+. Water resistance Insoluble at 210F.

Norma-Hoffman oxidation test (hours 265.

to p. s. i. drop at 210 F.).

The greases of Examples IV through VI were all dark brown, smoothuniform compositions and had free alkalinity values ranging from 0.25 to0.31% as NaOH.

The grease compositions of Examples I through VI above were comparedwith similar formulations employing furoic, levulinic and caproic acidand comparative data are set out in the table below. The formulation forthe three greases using furoic, levulinic and caproic acid is asfollows:

Basic formulation:

6.0% low molecular weight acid. 15.0% hydrogenated fish oil acids. 4.4%sodium hydroxide. 1.0% henyl-alpha-naphthylamine. 73.6 o mineral oil,viscosity 500 SUS at 100 F., 50 SUS at 210 F.

phenoxy acetic acid, beta-phenoxy propionic acid, and the like arecontemplated herein.

What is claimed is:

1. A lubricating grease composition consisting essentially of alubricating oil thickened to grease consistency with from 5% to 20% byweight of a mixture of from one to three parts of an alkali metal soapof a high molecular weight fatty acid and from one to two parts of analkali metal salt of a material having the formula Table COMPARATIVEDATA ON GREASES EMPLOYING LOW MOLECULAR WEIGHT ACID SALTS EthoxyP-methoxy P-ethoxy Phenoxy B-phenoxy F Propionic Benzolc Benzoic AceticPrcpionic Lewltmlc Ca roic Acid Acid Acid Acid Acid Acid Acld A019 pPercent FreeAlkalinity 0.12 0.3 0.29 0.25 0.31 0 25 worked t m narr. c200 0 210 215 Grease did not form. Structural Stability Penetration100,000 Strokes) 339 272 a 275 280 265 Dropping Point F.) 44c 45 500+500+ 500+ Dispersibility of Soap Excellent Excellent, Excel e tExcellent. Excellent Wheel Bearing Test (6 hours at 220 F.) Pass 1. PassPass Pass Pass The above results show that the sodium soap or lowmolecular weight oxy acids according to this invention in combinationwith the sodium soap of hydrogenated fish oil acids are easy to disperseand give excellent greases of high dropping point and structuralstability.

In a copending application, Serial No. 182,886, filed for the sameinventors on September 1, 1950, now Patent No. 2,623,854 issued December30, 1952, there is claimed grease compositions containing low molecularweight oxy acid salts, that is, alkyl oxy alkyl acid salts. Thisapplication, a continuation-in-part of that application is directedtoward the carboxyl derivatives of an alkyl aryl ether corresponding tothe formula where R and R are either aliphatic radicals containing from1 to 5 carbon atoms or aromatic radicals containing from 6 to 10 carbonatoms. In other words there is claimed herein grease compositionscontaining an alkali metal salt of a carboxyl derivative of an alkylaryl ether wherein the alkyl portion of the ether contains from 1 to 5carbon atoms and the aryl portion contains from 6 to 10 carbon atoms.Compounds such as p-methoxy benzoic acid p-ethoxy benzoic acid,

of aliphatic substantially saturated fatty acids, having an averagecarbon chain length within a range of from 12 to 22 carbon atoms andfrom 2% to 15% by weight of an alkali metal salt of a material havingthe formula wherein R is an alkyl group, containing from one to twocarbon atoms.

5. A lubricating composition according to claim 4 wherein said materialof the formula is phenoxyacetic acid.

6. A lubricating grease composition according to claim 4 wherein saidmaterial of the formula is beta phenoxy propionic acid.

References Cited in the file of this patent UNITED STATES PATENTS

1. A LUBRICATING GREASE COMPOSITION CONSISTING ESSENTIALLY OF ALUBRICATING OIL THICKENED TO GREASE CONSISTENCY WITH FROM 5% TO 20% BYWEIGHT OF A MIXTURE OF FROM ONE TO THREE PARTS OF AN ALKALI METAL SOAPOF A HIGH MOLECULAR WEIGHT FATTY ACID AND FROM ONE TO TWO PARTS OF ANALKALI METAL SALT OF A MATERIAL HAVING THE FORMULA